The availability of a large collection of mutants for the anthranilate synthetase - phosphoribosyl transferase (AS-PRT) enzyme complex of Salmonella typhimurium makes it possible to initiate an in- depth study into the relation between structure and function of this enzyme complex. We intend to use these mutants in order to obtain detailed information about the following parameters: location of specific ligand binding sites in the primary structure of the polypeptides; location of regions required for specific binding between the constituent polypeptides; investigation of the manner in which conformational changes induced in one component of the multienzyme complex are transmitted to the other component, etc. - Specific objectives for the duration of this grant period include the study of the AS-PRT complex in a mutant which requires anthranilate for growth, yet excretes it into the culture medium; a mutant hypersensitive to tryptophan inhibition; and several deletion mutants which produce fused AS-PRT peptides. Specific kinetic measurements will be made which are known to be highly sensitive to the state of aggregation of the enzyme components. This project will be a combined undertaking between a geneticist and an enzymologist.